It has recently been discovered that a mixture, comprising a sulfone compound and a hydrogen halide compound, can be an effective catalyst for use in the alkylation of olefin hydrocarbons by isoparaffin hydrocarbons to produce an alkylate reaction product, or alkylate. The alkylate reaction product generally contains hydrocarbons having seven or more carbon atoms, and it is a highly desirable gasoline blending component because of its high octane value as a motor fuel.
While a process which utilizes a catalyst composition comprising a sulfone component and a hydrogen halide component produces an alkylate product of very high quality, one side effect from using such a process in the production of alkylate is the formation of certain polymeric reaction by-products such as those referred to as acid-soluble oils, or ASO. These polymeric reaction by-products are referred to as acid-soluble oils because they are soluble in the catalyst utilized in the alkylation process and, thus, remain in the catalyst phase when the alkylate product resulting from the contact of a hydrocarbon mixture with an alkylation catalyst is separated from the alkylation catalyst. In an alkylation process which continuously separates the catalyst phase from the alkylation reaction product for reuse in the process reaction zone, there is a buildup of ASO in the catalyst. Over time, the ASO concentration will reach unacceptable concentration levels if not removed. A low concentration of ASO in the alkylation catalyst comprising a sulfone component and a hydrogen halide component is believed to have a beneficial effect upon the alkylation process or its product. However, higher concentrations of ASO in the alkylation catalyst have an adverse effect upon the catalyst activity and the final alkylate end-product. An ASO concentration in the alkylation catalyst that exceeds certain acceptable limits will result in lowering the octane of the alkylate end-product with incremental increases in the ASO concentration causing incremental decreases in-the alkylate octane.
In a continuous alkylation process which uses a catalyst having a sulfolane component and a hydrogen fluoride component, there can be an undesirable accumulation over time of water within the catalyst. This accumulation can result from the water that is contained within an alkylation feed, but it primarily results from the addition of the make-up catalyst components which generally contain concentrations of water. Particularly, the make-up sulfolane component of an alkylation catalyst often contains a significant concentration of water which, as has recently been discovered, will accumulate with:[.n the catalyst phase contained in the alkylation process system. While a small concentration of water within the alkylation catalyst phase may provide certain benefits, a too high concentration of water can have detrimental affects upon the alkylation process and its products. Thus, it is important for an alkylation process which uses a catalyst comprising sulfolane and hydrogen fluoride to have the ability to control the concentration of water contained in the catalyst.
In conventional alkylation processes that use a substantially pure hydrogen fluoride (tF) material as a catalyst, as opposed to the use of the aforementioned catalyst mixture comprising a sulfone component and a hydrogen halide component, there are certain known methods used to remove the ASO and water from the tIF catalyst used in a continuous alkylation process. Particularly, enough of a portion of the HF catalyst that is utilized in the conventional alkylation process is treated, or regenerated, so as to remove an amount of ASO and water at a rate that approximates the rate of accumulation of ASO and water in the alkylation catalyst. This is done by passing a portion of the HF catalyst to s stripping vessel, whereby the HF is stripped from the ASO by means of a vaporous hydrocarbon such as isobutane. The HF passes as a part of the vaporous overhead stream from the stripping vessel, and the ASO and water passes as a bottoms stream from the stripping vessel for further processing.
While the conventional alkylation catalyst regeneration techniques have worked well in the regeneration of the conventional HF catalyst, conventional means cannot be used -to regenerate an alkylation catalyst mixture which includes a sulfone component. This is because the boiling range of ASO overlaps the boiling temperatures of certain sulfones such as sulfolane. Also, the azeotropic properties of water and hydrogen fluoride impact the ability to separate water from the sulfolane and hydrogen fluoride catalyst. Therefore, simple distillation or stripping techniques as are used to separate HF from ASO cannot be used to effectively regenerate a sulfone-containing alkylation catalyst. Additionally, it is necessary to separate ASO from the sulfone in order to reclaim it for reuse as a catalyst in the alkylaltion process.